The present invention relates to a sputter and particularly a magnetic control oscillation-scanning sputter for improving magnetic field distribution.
Sputtering is a semiconductor manufacturing process for depositing a metal film. The main principle of sputtering is to introduce plasma ions into the chamber of the sputter and accelerate the ion""s speed to bombard a sputtering target, and then the target atoms on the surface of the sputtering target are blasted and scattered to deposit a metal film.
Referring to FIG. 1A for a conventional magnetic control oscillation-scanning sputter 10. The sputter 10 includes a chamber 11, a sputtering target 18, a base 13 and an elongated magnet 14. The sputtering target 18 includes a back plate 12 and a target 16. A substrate 15 is provided on the top of the base 13. The chamber 11 is vacuumized by a vacuum pump (not shown in the drawing). Charged plasma ions are introduced into the chamber, preferably, the charged plasma ions are argon ions with positive charges. The sputtering target 18 and the base 13 are connected respectively to a negative and a positive electrode to generate an electric potential gradient driving the positive argon ions to bombard the target 16 on the surface of the sputtering target 18. As a result, the atoms of the target 16 are deposited on a substrate 15 to form a film. The substrate 15 would be a wafer or a glass. The elongated magnet 14, as shown in FIG. 1B, is located on the rear side of the sputtering target 18. The elongated magnet 14 is moved and scanned reciprocately on the back side of the sputtering target 18 to control magnetic field strength to improve the uniformity and speed of film deposition on the surface of the substrate 15.
Referring to FIGS. 2A and 2B for the analysis of the deposited film on the substrate surface and the erosion condition on the target surface. The above-identified two figures indicate that conventional sputter still have following shortcomings:
1. non-uniformity of the film deposition: the testing result presents that the two end of the film is deposited on the substrate surface by a sputtering process which has a lower resistance Rs comparing to the resistance of the center portion. According to the equation, Resistance (Rs)=Resistance coefficient (e)/Film thickness, aforesaid phenomenon indicates that the thickness of two sides is greater than the thickness of center portion. The quality of the film is determined by the uniformity of resistance Rs or film thickness.
2. low utilization rate of the sputtering target: the sputtering target includes the back plate and the target. The front surface of the sputtering target possessing an uniform thickness before sputtering. After bombarding by plasma ions, the target is gradually eroded and consumed. When the erosion occurs uniformly, the sputtering target can achieve a higher utilization rate. However, according to conventional techniques, two sides of the sputtering target corresponding to two ends of the magnet is eroded. Once the erosion reaches the back plate of the sputtering target, the sputtering target becomes useless and must be discarded.
The disadvantages mentioned above are caused by stronger magnetic field intensity at two ends of the elongated magnet. As a result, a greater erosion rate occurs at the two sides of above target while bombarding. Therefore, the thickness of above deposited film at two sides is greater than the thickness of the film at the center portion, and results in uniform resistance distribution on the surface of the substrate.
Therefore, to overcome the problems set forth above to increase the utilization rate of the sputtering target, and to achieve uniform thickness and resistance distribution for the deposited film on the substrate surface has become a important pursued issue in semiconductor manufacturing field.
Therefore the primary object of the invention is to provide a magnetic control oscillation-scanning sputter to improve the distribution of the magnetic field intensity. An improved elongated magnet is provided to distribute the magnetic field intensity uniformly, thereby to increase the utilization rate of the sputtering target and achieve uniform thickness and resistance distribution for the deposited film on the substrate surface.
The sputter according to the invention includes a chamber which contains a sputtering target, a base and an elongated magnet. The chamber is vacuumized by a vacuum pump. Charged plasma ions (such as argon ions with positive charges) are introduced into the chamber. The sputtering target and the base are connected respectively to a negative and a positive electrode to form an electric potential gradient to drive the positive argon ions to bombard the target located on the surface of the sputtering target. As a result, the atoms of the target are deposited on a substrate which is located on the surface of the base to form a film. The substrate, preferably, is composed of a wafer or a glass. The elongated magnet is located on the rear side of the sputtering target and is moved and scanned reciprocately on the back side of the sputtering target to provide magnetic control to improve the uniformity and speed of film deposition.
The elongated magnet of the invention has magnetic erasing means located at two ends of the magnet to reduce the magnetic field intensity of the two ends so that the magnetic field intensity of the entire magnet is distributed uniformly. Therefore non-uniformity erosion of the sputtering target during sputtering process is prevented, and utilization rate of the sputtering target is increased, and more uniform distribution of the thickness and resistance of the deposited film are achieved to improve the sputter quality. The magnetic erasing means used in the invention is composed of magnetic materials such as iron, cobalt, or nickel. Furthermore, the surface of the magnetic erasing means, preferably, is plated with chrome for preventing rusting. The magnetic erasing means can be formed in a double-hook or a dog bone shape, and is tapered from two ends towards the center to distribute the magnetic field intensity uniformly through out the entire elongated magnet.
The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.